Emerson PNC001-A Series Important Product Information page 18

GFK-2573AB
Issue
Unexpected Loss of Device
faults
Unintended operation of
PNIO_DEV_COMM function
block
IOC SW Fault with large
configurations
The Push and Hold behavior of
the PNC001 Restart
Pushbutton results in the
CRU320 taking up to 1 second
to detect that PNC001 is no
longer available
Breaking and reconnecting an
MRP ring by pulling either of
the two MRM ports of the
PNC001 causes extra ring
open/close faults
Description
Loss of Device faults for currently connected devices may appear in the PLC I/O
Fault table and/or PNC001 local log when the PNC001 is reset via its reset
pushbutton.
The power flow output of the PNIO_DEV_COMM function block provides
validation of the input parameters and confirms that the PNC001 has locally
processed the configuration of the specified I/O Device. As currently
implemented, the power flow output will not turn ON until after the PNC001
has made its first attempt to connect to the specified I/O Device. Therefore, we
recommend the user not rely on power flow output for parameter validation.
When storing a configuration to the PNC001 that is close to the upper limit of
the controlling PLC's user memory, the store may fail with an IOC SW Fault
logged in the PLC's I/O Fault table. The workaround to resolve this issue is to
clear the PLC's existing configuration and store the configuration again.
When the PNC001 reset button is held down for more than 1 second, the
CRU320 can take up to 1 second to detect the loss of the PNC001 (after the
PNC001 module resets). This causes a delay in the CPU signaling the Loss of IOC,
and in taking the appropriate fault actions (setting point faults, stopping the
controller if Loss of or Missing I/O Controller faults are configured as Fatal, etc.)
In a Hot Standby Redundancy System, if the system is synchronized and the
PNC001 in question is in the active unit, this also causes a delay in the
redundant system failing over to the backup unit. If this delay exceeds the
Redundancy Data Hold Time (RDHT) for a given I/O Device, that IO Device will
disconnect from the backup unit before the failover occurs.
It is not recommended to use the PNC001 reset button in a normal operating
system. If the reset button must be used, it is recommended to first attempt a
brief press and release of the PNC001 reset button (the PNC001 should reset as
soon as the button is released). Only if the first attempt fails should the PNC001
button be depressed until the PNC001 resets (approximately 2-3 seconds).
In some cases, if the network is broken and repaired at either of the two ring
ports of a PNC001 configured to be the MRM, an extra I/O Bus Fault-Redundant
Ethernet network ring is broken (open) and the I/O Bus Fault-Redundant
Ethernet network ring okay (closed) faults are logged in both the I/O Fault
Table and the PNC001 Local Log when the ring is repaired.
These additional faults can safely be ignored as long as the last fault to be
logged is the I/O Bus Fault-Redundant Ethernet network ring okay (closed).
Additional verification of ring status can be obtained by issuing a show rdnMedia
command using the PNC001's CLI interface.
Jul 2022
16